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#346307 - 04/27/11 04:08 AM More amp woes
CV Offline
Founder, Axiom Upgrade Club
shareholder in the making

Registered: 07/20/06
Posts: 11675
Loc: Richland, WA, USA
I got my repaired A1400-8 back from Axiom yesterday. It was nice to see it come back. Unfortunately, the loud humming it was exhibiting prior to failure of one of the channel pairs is still there. It's distractingly loud. Sometimes it lessens briefly, but it always increases again. I'm assuming it's an amp issue. Taking it out of the chain makes it disappear, and it persisted before when I switched from my pre-pro with balanced connections to an A/V receiver with unbalanced connections. It really is a loud hum. I'm going to be disconnecting the amp again, even though I'd really like to be using it. If any of you have any ideas, though, I'm all ears.

Because of the issues, it's getting harder to justify external amplification. I still want it, but the new Onkyo receiver has actually been doing a pretty good job. I'd still like extra power potential for my mains and center(s), but that's all. I may stick with receivers instead of pre-pros from now on. The receiver can power the remaining surround/wide/height speakers. I'm hoping Axiom lets me "upgrade" from this 8-channel amp to two of the 2-channel amps whenever they (hopefully) start offering amps again. I think that will be the way to go. If not Axiom, then maybe when the Outlaw monoblocks are on special sometime I'll pick up some of those, unless something shinier catches my eye.

Anyway, I just wanted to vent a little and possibly get some suggestions. Thanks for listening!

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#346313 - 04/27/11 07:45 AM Re: More amp woes [Re: CV]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13565
Loc: Iowa
What if you unplug everything else in your system, except the pre and amp, no other equipment?
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M80s-VP180-4xM22ow-4xM3ic-EP600-2xEP350
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#346316 - 04/27/11 08:17 AM Re: More amp woes [Re: SirQuack]
a401classic Offline
connoisseur

Registered: 11/29/06
Posts: 1328
Loc: Alpharetta, GA
All my humming issues were solved by one or the combination of 3 things, in no particular order;

* Ground loop isolator on the cable line.

* Removing the ground screw from the back of my EP500

* Making sure all the plugs for my A/V system were on the the same circuit or at least the hot wire was on the same leg in the breaker box (i.e. every other breaker in a normal US house, or every third breaker for those fortunate enough to have 3 phase power at home)

Just thought of a 4th hum, recently solved. When connecting video output from my laptop, I had to eliminate the ground leg on the power converter (3 to 2 adapter plug)

I have not reas through all your amp woes, but I would guess that you've already covered those bases...
_________________________
Scott

My HT

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#346323 - 04/27/11 09:08 AM Re: More amp woes [Re: CV]
Adrian Offline
axiomite

Registered: 12/27/08
Posts: 6865
Loc: It's all about the location.
Sorry to hear about your amp woes, Charles. I hope Axiom makes things right for you.
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Half of communication is listening. You can't listen with your mouth.

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#346417 - 04/27/11 09:34 PM Re: More amp woes [Re: CV]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10621
Charles, I don't really have any new suggestions, since if the speakers hum with the A1400-8 powering them, but not with the Onkyo receiver, there's no ground loop question, but as you suspect, an amplifier problem. The power supply section of amplifiers, in particular the rectifier and filter capacitors, is supposed to provide clean DC free of audible hum when operating correctly. When you sent it in for repair of the dead output channels did you also describe the hum problem?
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#346426 - 04/28/11 12:06 AM Re: More amp woes [Re: JohnK]
CV Offline
Founder, Axiom Upgrade Club
shareholder in the making

Registered: 07/20/06
Posts: 11675
Loc: Richland, WA, USA
Looking back through my correspondence, it doesn't look like I did mention the hum. It must be because I hadn't really nailed down what was causing the hum. JC says that the unit would have been fully tested, and they should have caught the hum. In any case, they're aware now, and he's asking around for other things to try.

Okay, there's no hum if I have nothing hooked up to the amp, but with the amp still hooked up to the speakers. Does that mean anything? I'm thinking I need to borrow back the pre-pro I gave away and make sure that having it hooked up with the balanced connections still creates the hum.

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#346428 - 04/28/11 12:16 AM Re: More amp woes [Re: CV]
ClubNeon Offline
connoisseur

Registered: 02/06/09
Posts: 3466
Loc: Western Maryland, USA
Did you try a hooking up a battery powered, portable music player to the amp? Start with the volume all the way down to be safe.
_________________________
Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs
-Chris

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#346429 - 04/28/11 12:19 AM Re: More amp woes [Re: ClubNeon]
CV Offline
Founder, Axiom Upgrade Club
shareholder in the making

Registered: 07/20/06
Posts: 11675
Loc: Richland, WA, USA
I'll try that out.

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#346432 - 04/28/11 12:33 AM Re: More amp woes [Re: CV]
CV Offline
Founder, Axiom Upgrade Club
shareholder in the making

Registered: 07/20/06
Posts: 11675
Loc: Richland, WA, USA
With my portable player, the hum is still there, but not as strong. Hooking the receiver back up, the hum is definitely louder, but it's not as loud as it has been. Right now I would still consider it too loud, but at least now it could be drowned out at decent listening levels.

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#346433 - 04/28/11 12:35 AM Re: More amp woes [Re: CV]
ClubNeon Offline
connoisseur

Registered: 02/06/09
Posts: 3466
Loc: Western Maryland, USA
Since it hums with a portable player that's not connected to a ground, it is definitely not a ground loop.
_________________________
Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs
-Chris

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